Electrochemical analysis method using boron-doped electroconductive diamond electrode

Abstract

This invention provides an electrochemical analysis method for accurately detecting a harmful substance such as arsenic contained in a solution. In the electrochemical analysis method, a working electrode and a counter electrode are disposed in an object electrolytic solution. A negative potential is applied to the working electrode to electrodeposit the electrolyte onto the surface of the working electrode and thus to form an electrodeposit. Next, the potential of the working electrode is sweeped in a positive potential direction to allow the electrodeposit to elute into the solution and, at the same time, to detect a current change upon a potential change and thus to analyze an object substance dissolved as an electrolyte in the object electrolytic solution. A boron-doped electroconductive diamond electrode or an electrode with gold deposited on its surface is used as the working electrode.

1. An electrochemical analysis method comprising:
 arranging a working electrode and a counter electrode in an electrolyte solution to be measured, wherein the working electrode is a boron-doped electroconductive diamond electrode and the electrolyte solution to be measured contains electrolytes including element (M1), which is a low-oxidation state of element (M) and electrolytes including element (M2) which is a high-oxidation state of element (M); 
 applying a negative potential to the working electrode so that the element (M2) is electrodeposited on a surface of the working electrode to cause an electrodeposition reaction and form an electrodeposit; 
 maintaining the potential of the working electrode at an electrodeposition potential of the element (M1), after the step of applying the negative potential; and 
 sweeping the potential of the working electrode toward a positive potential, after the step of maintaining the potential of the working electrode, to thereby elute the electrodeposited element (M1), while detecting electric current changes in response to potential changes to thereby analyze a substance to be measured, the substance being dissolved as the element (M) of the electrolyte in the electrolyte solution to be measured. 
 
     
     
       2. An electrochemical analysis method according to  claim 1 , wherein the element (M) is arsenic (As), the element (M1) is As(III) and the element (M2) is As(V). 
     
     
       3. An electrochemical analysis method comprising:
 arranging a working electrode and a counter electrode in an electrolyte solution to be measured that contains electrolytes including element (M1), which is a low-oxidation state of element (M) and element (M2), which is a high-oxidation state of element (M), wherein the working electrode is a boron-doped electroconductive diamond electrode; 
 applying a negative potential to the working electrode so that the electrolyte is electrodeposited on a surface of the working electrode to form an electrodeposit; and 
 sweeping the potential of the working electrode toward a positive potential, after the step of applying the negative potential, to thereby elute the electrodeposit in the solution while detecting electric current changes in response to the potential changes to thereby analyze a substance to be measured which is dissolved as the electrolyte in the electrolyte solution to be measured, 
 wherein the following analyses (1) and (2) are conducted on the electrolyte solution to be measured, the analysis value for the element (M2) being obtained from the analysis value for the element (M1) obtained by analysis (1) and the analysis value for the element (M) obtained by analysis (2): 
 (1) applying the negative potential to electrodeposit the element (M1) to the working electrode to thereby electrodeposit the element (M1) on the working electrode;
 sweeping the potential toward a positive potential, after the step of applying the negative potential, to thereby elute the electrodeposited element (M1) while detecting electrical current changes in response to potential changes to thereby analyze the element (M1) which is dissolved as an electrolyte in the electrolyte solution to be measured, and 
 
 (2) applying the negative potential to electrodeposit the element (M2) to the working electrode to thereby cause an electrodeposition reaction;
 maintaining the potential of the working electrode at an electrodeposition potential of the element (M1), after the step of applying the negative potential; 
 sweeping the potential toward the positive potential to thereby elute the electrodeposited element (M1) while detecting electrical current changes in response to potential changes to thereby analyze the element (M) which is dissolved as an electrolyte in the electrolyte solution to be measured. 
 
 
     
     
       4. An electrochemical analysis method according to  claim 3 , wherein the element (M) is arsenic (As), the low-oxidation element (M1) is As(III) and the high-oxidation element (M2) is As(V).